The present invention relates to methods of manufacturing an antivibration device for motor vehicles, the device comprising at least one metal insert for bonding to an elastomer.
The term xe2x80x9cmetal insertxe2x80x9d is used herein to mean any piece made of metal for bonding to elastomer, and regardless of whether or not the piece is for embedding in the elastomer.
More particularly, the invention relates to a method of manufacturing an antivibration device for motor vehicles, the device comprising at least one metal insert itself having at least one fixing surface bonded to an elastomer (e.g. rubber), the method comprising the following steps:
a step of cleaning the fixing surface;
a coating step during which the fixing surface is covered in at least one layer of fixing material for making a bond between the insert and the elastomer, said material being based on rubber; and
a step of molding the elastomer onto the insert.
During the coating step it can be deposited in particular:
an activatable primary adhesive which is subsequently covered in a layer of secondary adhesive, which secondary adhesive subsequently reacts with the elastomer while the elastomer is being vulcanized; or
directly an adhesive which reacts on its own with the elastomer during vulcanization thereof (in which case it is constituted by the adhesive referred to as xe2x80x9csecondaryxe2x80x9d in the paragraph above).
In known methods of this type, the cleaning step consists in particular of dipping the metal insert in successive degreasing baths which require bulky and expensive infrastructure and which contain substances that are dangerous and polluting.
A particular object of the present invention is to mitigate those drawbacks.
For this purpose, according to the invention, in a method of the kind in question, the cleaning step is performed dry and comprises laser treatment which consists in scanning the fixing surface with a laser beam of sufficient power to eliminate the impurities present on said fixing surface.
By means of these provisions, there is no need to use degreasing baths for cleaning the surface of the insert, thereby simplifying the method of treatment, and making it less expensive and less dangerous for the environment. In addition, it is found that laser treatment also facilitates subsequent bonding of the insert with the elastomer. The fact that the fixing material is based on rubber also facilitates bonding with the elastomer.
In different implementations of the invention, use may also be made of one or more of the following provisions:
during the cleaning step, the laser beam delivers energy to the fixing surface at a mean density per unit area lying in the range 0.5 Joules per square centimeter (J/cm2) to 20 J/cm2;
a pulse laser is used;
the fixing surface is scanned by the laser beam at a treatment speed of at least 2 square centimeters per second (cm2/s);
a laser is used selected from excimer lasers emitting in the ultraviolet and yttrium aluminum garnet (YAG) lasers emitting in the infrared;
the insert is made of steel;
during the cleaning step the laser beam is used to deliver sufficient energy to the fixing surface of the metal insert to eliminate all traces of corrosion on said fixing surface;
the cleaning step is followed by a passivation step;
the cleaning step is followed directly by the coating step;
the coating step is implemented sufficiently quickly after the cleaning step to avoid any trace of corrosion reappearing on the fixing surface;
the coating step is implemented less than 24 hours after the end of the cleaning step;
during the cleaning step the laser beam is used to deliver sufficient energy to the fixing surface to etch said fixing surface to a small extent: in any event, this facilitates subsequent adhesion between the insert and the elastomer; in addition, this avoids a subsequent shot blasting step of the kind normally performed between the cleaning step and a step of applying anticorrosion protection; and
the elastomer is rubber.